Entity Framework Code-First - Define the key for this EntityType

Question

Hi I'm planning to test EF Code First in one of my project. This is what I want actually. I have three tables and the structure is as follows

public partial class App_user     {         public int id { get; set; }         public string name { get; set; }         public string email_address { get; set; }         public string password { get; set; }         public int user_type { get; set; }         public List<Role> Roles { get; set; }     }  public partial class Role     {         public int id { get; set; }         public string name { get; set; }     } public partial class User_role     {         public int user_id { get; set; }         public int role_id { get; set; }         public virtual Role Role { get; set; }         public virtual App_user App_user { get; set; }     } 

In the third table there is no primary key. So it gives an error while running. Here is the error message -

System.Data.Edm.EdmEntityType: : EntityType 'User_role' has no key defined. Define the key for this EntityType. System.Data.Edm.EdmEntitySet: EntityType: The EntitySet User_roles is based on type User_role that has no keys defined.

Why its is happening? Is there a solution for this?

Answer 1

If think you are trying to model many-to-many relation between user and role. In such case your model is completely wrong.

Use this instead:

public partial class App_user {     public int id { get; set; }     public string name { get; set; }     public string email_address { get; set; }     public string password { get; set; }     public int user_type { get; set; }     public virtual ICollection<Role> Roles { get; set; } }  public partial class Role {     public int id { get; set; }     public string name { get; set; }     public virtual ICollection<User> Users { get; set; } } 

This will create many-to-many automatically and you will not need to bother with junction table. If you need to expose junction table you must use this:

public partial class App_user {     public int id { get; set; }     public string name { get; set; }     public string email_address { get; set; }     public string password { get; set; }     public int user_type { get; set; }     public virtual ICollection<User_Role> UserRoles { get; set; } }  public partial class Role {     public int id { get; set; }     public string name { get; set; }     public virtual ICollection<User_Role> UserRoles { get; set; } }  public partial class User_role {     [Key, ForeignKey("App_user"), Column(Order = 0)]     public int user_id { get; set; }     [Key, ForeignKey("Role"), Column(Order = 1)]     public int role_id { get; set; }     public virtual Role Role { get; set; }     public virtual App_user App_user { get; set; } } 

Exposing junction table is meaningless if you don't need additional properties in it.

To your error - each entity in Entity framework must have primary key defined.

Answer 2

You can simply do like this:

public partial class User_role {     [Key]     public int user_id { get; set; }     [Key]     public int role_id { get; set; }     public virtual Role Role { get; set; }     public virtual App_user App_user { get; set; } }